Microwave technology used for plasma diagnostic in complicated situations

In this paper, the microwave technology has been applied to measure the plasma parameters in large-volume AC glow discharge with coaxial gridded hollow electrodes. By measuring the phase shift of microwave through the plasma, the characteristics of the plasma density changing with the input power in hollow ac discharge plasma has been confirmed. The phase shift of the microwave is determined by vector network analyzer (PNA-N5234A) with antennas, and the selected microwave frequency is 30GHz. Then, the experimental results are compared with the theoretical results and are in good agreement. Additionally, using the improved probe technology, the plasma parameters also are obtained by probe diagnostics. And the probe results are compared to the microwave technology, which indicates that in the AC glow discharge the microwave diagnostic is more stable and accurate.